Breathing Patterns and Dental Development
Causes — Chronic mouth-breathing can be caused by chronic nasal obstruction/congestion
(eg, from allergies or asthma), swollen adenoid glands or tonsils, or anatomic abnormalities (eg, cleft lip/palate), or it may be a learned habit. The prevalence of chronic mouth-breathing among children ranges from 9 percent of four year- olds to 40 percent of first-graders.
Dental effects — Several, but not all, studies suggest that chronic mouth-breathing
can sometimes lead to long, narrow faces. The primary dental effects of chronic mouth-breathing include narrowing of the upper jaw, over-eruption of the permanent molars, and downward and backward growth of the mandible. These effects are mediated through the altered tongue position and the openmouth posture.
Narrow upper jaw — Upper jaw width is reduced (resulting in posterior crossbite) in
children who are chronic mouth-breathers, The narrow upper jaw in chronic mouth-breathers is related to the position of the tongue. In normal nasal breathing, the tongue
rests against the palate where it exerts lateral pressure and plays an important role in the
widening of the maxillary arch. In contrast, in mouth-breathing, the tongue rests lower in the mouth and thus exerts less lateral pressure on the upper teeth. This makes the upper jaw grow narrower.
Over-eruption of Teeth — Permanent teeth typically continue to erupt until they make
contact with teeth or tissue in the opposing jaw. Because this contact is missing in chronic
mouth-breathers, over-eruption of the permanent molars may result. Over-eruption of the
permanent molars can lead to backward growth of the lower jaw, resulting in
increased height of the lower face and a shorter lower jaw.
Management — Orthodontists and Ear, nose and throat doctors recommend early and aggressive treatment, including referral to an otolaryngologist if necessary, for any respiratory or anatomic problem that predisposes a young child to a mouth-breathing pattern
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